4G8 ON THE ARTIFICIAL CULTURE OF MARINE PLANKTON ORGANISMS. 



flask in 800 c.c. of "outside" water, which had been sterilized by heating 

 and then treated with animal charcoal and filtered. About 1 c.c. of 

 fine plankton, containing diatoms, was added to the flask on May 12th. 

 On May 25tli some of the water was poured off and a new supply 

 added. As the amount of food seemed small, some culture of a green 

 alga {PIcurococcus mucosus (Kutz.), IJabenh.) was added, and this con- 

 tinued to grow well in the flask. The larvte continued healthy and 

 formed young Giicumaria^oi which many were still alive on July 25th, 

 1907, i.e. fourteen months after fertilization. Some of the water was 

 changed in this flask on May 30th, 1906, June 18th, 1906, September 

 loth, 1906, and July 25th, 1907. Although many of these Cvcicmaria 

 remained quite healthy they did not grow to any great size. Probably 

 the food which was suitable to the larvie and early stages, ought 

 to have been changed as the animals grew older. 



Pomatoccros triqucter. Tlie larvic of Po/natocci-os are perhaps the 

 easiest to rear, and give the most certain results of any with which we 

 have experimented. They do well on the minute variety of Nitzscliia 

 dosteriitvi, but will feed upon almost any small diatom. Since the 

 adults live in calcareous tubes attached to stones, and the tubes have 

 to be broken open before the eggs can be obtained, it is not easy to get 

 the latter free from infection of other organisms. If, therefore, the 

 eggs are fertilized and placed in sterilized animal-charcoal water with 

 only moderate precautions, sufficient growth of diatoms or other 

 organisms will generally take place in the jar to feed the larvai and 

 bring them to the adult state. When once fixed to the glass tlie 

 worms are very hardy and healthy, and a stream of ordinary aquarium 

 water can be run through the jar. They then grow rapidly and attain 

 a size equal to any found on the shore. The follovv-ing experiment may 

 be given in detail to illustrate the time occupied in development. On 

 August 29th, 1907, eggs of Pomatoceros trvpider were fertilized in 

 animal-charcoal Berkefeld water, and some pure culture of Nitzsdiia 

 closterium, var., added. The larvre fed well, and on October 1st (i.e. 

 thirty-three days after fertilization) a great number had fixed on the 

 sides of the jar and made quite normal tubes. A constant stream of 

 the ordinary aquarium water was then allowed to run through the jar, 

 and the worms continued to grow and flourish, reaching a large size, 

 and are still alive and healthy (November, 1909). A similar result 

 was obtained from the same batch of eggs by feeding on a pure culture 

 of a flagellate infusorian. Temperatures during these two experiments 

 were between 15° C. and 19° C. 



Chactoptcrns variopedatnu. Four experiments were made with tin's 



